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Task/Matrix-multiplication/REXX/matrix-multiplication.rexx

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+/*REXX program calculates the Kronecker product   of   two arbitrary size   matrices. */
+Signal On syntax
+x.=0
+amat=4X2 1 2 3 4 5 6 7 8         /* define A matrix size and elements */
+bmat=2X3 1 2 3 4 5 6             /* "      B    "     "   "     "     */
+Call makeMat 'A',amat            /* construct A matrix from elements  */
+Call makeMat 'B',bmat            /* "         B    "     "     "      */
+If cols.A<>rows.B Then
+  Call exit 'Matrices are incompatible for matrix multiplication',
+            'cols.A='cols.A'<>rows.B='rows.B
+Call multMat                     /* multiply A x B                    */
+Call showMat 'A',amat            /* display matrix A                  */
+Call showMat 'B',bmat            /* "          "   B                  */
+Call showMat 'C',mm              /* "          "   C                  */
+Exit
+/*--------------------------------------------------------------------*/
+makeMat:
+  Parse Arg what,size elements   /*elements: e.1.1 e.1.2 - e.rows cols*/
+  Parse Var size rows 'X' cols
+  x.what.shape=rows cols
+  Parse Value rows cols With rows.what cols.what
+  n=0
+  Do r=1 To rows
+    Do c=1 To cols
+      n=n+1
+      element=word(elements,n)
+      x.what.r.c=element
+      End
+    End
+  Return
+/*--------------------------------------------------------------------*/
+multMat:
+/* x.C.*.* = x.A.*.* x x.B.*.*                                        */
+  Do i=1 To rows.A
+    Do j=1 To cols.B
+      Do k=1 To cols.A
+        x.C.i.j=x.C.i.j+x.A.i.k*x.B.k.j
+        End /*k*/
+      End /*j*/
+    End /*i*/
+  mm=rows.A||'X'||cols.B
+  Do i=1 To rows.A
+    Do j=1 To cols.B
+      mm=mm x.C.i.j
+      End /*j*/
+    End /*i*/
+  Call makeMat 'C',mm
+  Return
+/*--------------------------------------------------------------------*/
+showMat:
+  Parse Arg what,size .
+  Parse Var size rows 'X' cols
+  z='+'
+  b6=left('',6)
+  Say ''
+  Say b6 copies('-',7) 'matrix' what copies('-',7)
+  w=0
+  Do r=1 To rows
+    Do c=1 To cols
+      w=max(w,length(x.what.r.c))
+      End
+    End
+  Say b6 b6 '+'copies('-',cols*(w+1)+1)'+' /* top border              */
+  Do r=1 To rows
+    line='|' right(x.what.r.1,w)    /* element of first colsumn       */                       /* start with long vertical bar   */
+    Do c=2 To cols                  /* loop for other columns         */
+      line=line right(x.what.r.c,w) /* append the elements            */
+      End /* c */
+    Say b6 b6 line '|'              /* append a long vertical bar.    */
+    End /* r */
+  Say b6 b6 '+'copies('-',cols*(w+1)+1)'+' /* bottom border           */
+  Return
+exit:
+  Say arg(1)
+  Exit
+
+Syntax:
+  Say 'Syntax raised in line' sigl
+  Say sourceline(sigl)
+  Say 'rc='rc '('errortext(rc)')'
+  Say '***** There was a problem!'
+  Exit